Patrick Tonui - Academia.edu (original) (raw)
Papers by Patrick Tonui
This research focused on developing new organic and inorganic semiconductor materials and techniq... more This research focused on developing new organic and inorganic semiconductor materials and techniques for use in design and fabrication of organic photovoltaic solar cells. Despite OPVs having benefitted from material development and device preparation conditions optimization, the power conversion efficiency(PCE) of perovskite based solar cells LIST OF FIGURES xii
Nano Hybrids and Composites, 2018
Organic and inorganic nanocomposites have been successfully used in the preparation of thin film ... more Organic and inorganic nanocomposites have been successfully used in the preparation of thin film organic solar cells with the view either to enhance the harvesting of solar energy or to assist in the charge transport processes. The optical absorption, conductivity and environmental stability of the nanocomposite are the main criteria that determine the suitability of the material for solar energy application. This chapter discusses the properties of a number of nanocomposite which are widely used in the preparation of various types of thin film solar cells.
Journal of Physics and Chemistry of Solids, 2019
Environmentally stable and uniform silver:zinc bimetallic nano-composites (BNCs) was synthesized ... more Environmentally stable and uniform silver:zinc bimetallic nano-composites (BNCs) was synthesized by co-reduction of silver:zinc ions from silver and zinc nitrates. The synthesized nanocomposites were employed at the various layers of the device structure in the preparation of thin film peroveskite solar cell. Experimental evidences suggest that the nano-composite exhibited core-shell type structure which has important implication for surface plasmon resonance (SPR) absorption. It was found that enhanced photo-currents have been measured from solar cells by employing the Ag:Zn nano-particles as electron transport co-buffer layer. These resulted in improved power conversion efficiency and short current density by 26 % and 53 %, respectively. The information gathered from the optical measurements of the nano-particles suggest that significant quenches in photoluminescence(PL) intensity was measured from Ag:Zn composite compared to monometallic Ag and Zn nano-particles which is attributed to enhanced carrier density in bimetallic phases. Scanning and tunnelling electron spectroscopes (SEM and TEM) were employed to investigate morphology, crystallinity and elemental composition of the nano-particles.
Physica B: Condensed Matter, 2016
Understanding the phenomena at interfaces is crucial for producing efficient and stable flexible ... more Understanding the phenomena at interfaces is crucial for producing efficient and stable flexible organic solar cell modules. Minimized energy barriers enable efficient charge transfer, and good adhesion allows mechanical and environmental stability and thus increased lifetime. We utilize here the inverted organic solar module stack and standard photoactive materials (a blend of poly(3-hexylthiophene) and [6,6]phenyl C61 butyric acid methyl ester) to study the interfaces in a pilot scale large-area roll-to-roll (R2R) process. The results show that the adhesion and work function of the zinc oxide nanoparticle based electron transport layer can be controlled in the R2R process, which allows optimization of performance and lifetime. Plasma treatment of zinc oxide (ZnO) nanoparticles and encapsulation-induced oxygen trapping will increase the absolute value of the ZnO work function, resulting in energy barriers and an S-shaped IV curve. However, light soaking will decrease the zinc oxide work function close to the original value and the S-shape can be recovered, leading to power conversion efficiencies above 3%. We present also an electrical simulation, which supports the results. Finally, we study the effect of plasma treatment in more detail and show that we can effectively remove the organic ligands around the ZnO nanoparticles from the printed layer in a R2R process, resulting in increased adhesion. This postprinting plasma treatment increases the lifetime of the R2R printed modules significantly with modules retaining 80% of their efficiency for ∼3000 h in accelerated conditions. Without plasma treatment, this efficiency level is reached in less than 1000 h.
Renewable and Sustainable Energy Reviews, 2018
Perovskite based solar cells have recently emerged as one of the possible solutions in the photov... more Perovskite based solar cells have recently emerged as one of the possible solutions in the photovoltaic industry for availing cheap solution processable solar cells. Hybrid perovskites display special combination of low bulktrap densities, ambipolar charge transport properties, good broadband absorption properties and long charge carrier diffusion lengths, which make them suitable for photovoltaic applications. The year 2015 witnessed an upsurge in the published research articles on perovskite solar cells (PSC) which is indicative of the potential of this material. Since the introduction of PSC the power conversion efficiency has reached above 22% in a relatively short period of time. However, the poor reproducibility in device fabrication and lack of uniformity of the PSCs performances is a major challenge in obtaining highly efficient large scale PSC devices. The aim of this paper is to present a brief review on the current status of perovskites based solar cell due to the use of different device architectures, fabrication techniques as well as on the use of various electron and hole interfacial layers (HTMs and ETMs). The review also discusses the basic mechanisms for device operation which provides better understanding on the properties of the various layers of device structures.
Journal of Physics and Chemistry of Solids
Abstract Environmentally stable and uniform silver:zinc bimetallic nano-composites (BNCs) was syn... more Abstract Environmentally stable and uniform silver:zinc bimetallic nano-composites (BNCs) was synthesized by co-reduction of silver:zinc ions from silver and zinc nitrates. The synthesized nano-composites were employed at the various layers of the device structure in the preparation of thin film peroveskite solar cell. Experimental evidences suggest that the nano-composite exhibited core-shell type structure which has important implication for surface plasmon resonance (SPR) absorption. Enhanced photo-currents have been measured from solar cells by employing Ag:Zn nano-particles as electron transport co-buffer layer. Which resulted in improved power conversion efficiency and short current density by 26% and 53%, respectively. The information gathered from the optical measurements of the nano-particles suggest that significant quenches in photoluminescence(PL) intensity was measured from Ag:Zn composite compared to monometallic Ag and Zn nano-particles which is attributed to enhanced carrier density in bimetallic phases. Scanning and tunnelling electron spectroscopes (SEM and TEM) were employed to investigate morphology, crystallinity and elemental composition of the nano-particles.
Deafness or being hard of hearing is one of the major hindrance of effective communication betwee... more Deafness or being hard of hearing is one of the major hindrance of effective communication between the hearing and the deaf. A deaf person can neither hear his voice nor that of other people and therefore cannot develop meaningful speech or language. Being deaf or hard of hearing limits one from getting or giving information [13]. In Kenya there are over thirty primary schools for the deaf with an average of a hundred and eighty students or less and a few smaller units of between thirty and forty students. It was the purpose of this project to help design and simulate an alarm system that can help deaf and hard of hearing students improve communication with their teachers and the rest of the people. This is because deaf students can learn to speak and make themselves understood if properly taught by skilled parents and teachers through the senses of vibration, touch, visual aids, kinesthetic( combined sensations by which position, weight and muscular position are perceived) and prop...
Physica B: Condensed Matter, 2016
Abstract The effect of interfacial buffer layers in organic photovoltaic cell (OPV) whose active ... more Abstract The effect of interfacial buffer layers in organic photovoltaic cell (OPV) whose active layer is composed of poly(3 hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend was studied. The electrical properties of OPV devices produced with and without interfacial layers are compared and discussed in terms of measured parameters of the cells. The charge transport properties showed significant difference on the mobility and activation factor between the two types of device structures. The life time measurements in the unprotected conditions are also presented and discussed.
Nano Hybrids and Composites, 2018
Organic and inorganic nanocomposites have been successfully used in the preparation of thin film ... more Organic and inorganic nanocomposites have been successfully used in the preparation of thin film organic solar cells with the view either to enhance the harvesting of solar energy or to assist in the charge transport processes. The optical absorption, conductivity and environmental stability of the nanocomposite are the main criteria that determine the suitability of the material for solar energy application. This chapter discusses the properties of a number of nanocomposite which are widely used in the preparation of various types of thin film solar cells.
Optik - International Journal for Light and Electron Optics, 2016
Physica E: Low-dimensional Systems and Nanostructures
This research focused on developing new organic and inorganic semiconductor materials and techniq... more This research focused on developing new organic and inorganic semiconductor materials and techniques for use in design and fabrication of organic photovoltaic solar cells. Despite OPVs having benefitted from material development and device preparation conditions optimization, the power conversion efficiency(PCE) of perovskite based solar cells LIST OF FIGURES xii
Nano Hybrids and Composites, 2018
Organic and inorganic nanocomposites have been successfully used in the preparation of thin film ... more Organic and inorganic nanocomposites have been successfully used in the preparation of thin film organic solar cells with the view either to enhance the harvesting of solar energy or to assist in the charge transport processes. The optical absorption, conductivity and environmental stability of the nanocomposite are the main criteria that determine the suitability of the material for solar energy application. This chapter discusses the properties of a number of nanocomposite which are widely used in the preparation of various types of thin film solar cells.
Journal of Physics and Chemistry of Solids, 2019
Environmentally stable and uniform silver:zinc bimetallic nano-composites (BNCs) was synthesized ... more Environmentally stable and uniform silver:zinc bimetallic nano-composites (BNCs) was synthesized by co-reduction of silver:zinc ions from silver and zinc nitrates. The synthesized nanocomposites were employed at the various layers of the device structure in the preparation of thin film peroveskite solar cell. Experimental evidences suggest that the nano-composite exhibited core-shell type structure which has important implication for surface plasmon resonance (SPR) absorption. It was found that enhanced photo-currents have been measured from solar cells by employing the Ag:Zn nano-particles as electron transport co-buffer layer. These resulted in improved power conversion efficiency and short current density by 26 % and 53 %, respectively. The information gathered from the optical measurements of the nano-particles suggest that significant quenches in photoluminescence(PL) intensity was measured from Ag:Zn composite compared to monometallic Ag and Zn nano-particles which is attributed to enhanced carrier density in bimetallic phases. Scanning and tunnelling electron spectroscopes (SEM and TEM) were employed to investigate morphology, crystallinity and elemental composition of the nano-particles.
Physica B: Condensed Matter, 2016
Understanding the phenomena at interfaces is crucial for producing efficient and stable flexible ... more Understanding the phenomena at interfaces is crucial for producing efficient and stable flexible organic solar cell modules. Minimized energy barriers enable efficient charge transfer, and good adhesion allows mechanical and environmental stability and thus increased lifetime. We utilize here the inverted organic solar module stack and standard photoactive materials (a blend of poly(3-hexylthiophene) and [6,6]phenyl C61 butyric acid methyl ester) to study the interfaces in a pilot scale large-area roll-to-roll (R2R) process. The results show that the adhesion and work function of the zinc oxide nanoparticle based electron transport layer can be controlled in the R2R process, which allows optimization of performance and lifetime. Plasma treatment of zinc oxide (ZnO) nanoparticles and encapsulation-induced oxygen trapping will increase the absolute value of the ZnO work function, resulting in energy barriers and an S-shaped IV curve. However, light soaking will decrease the zinc oxide work function close to the original value and the S-shape can be recovered, leading to power conversion efficiencies above 3%. We present also an electrical simulation, which supports the results. Finally, we study the effect of plasma treatment in more detail and show that we can effectively remove the organic ligands around the ZnO nanoparticles from the printed layer in a R2R process, resulting in increased adhesion. This postprinting plasma treatment increases the lifetime of the R2R printed modules significantly with modules retaining 80% of their efficiency for ∼3000 h in accelerated conditions. Without plasma treatment, this efficiency level is reached in less than 1000 h.
Renewable and Sustainable Energy Reviews, 2018
Perovskite based solar cells have recently emerged as one of the possible solutions in the photov... more Perovskite based solar cells have recently emerged as one of the possible solutions in the photovoltaic industry for availing cheap solution processable solar cells. Hybrid perovskites display special combination of low bulktrap densities, ambipolar charge transport properties, good broadband absorption properties and long charge carrier diffusion lengths, which make them suitable for photovoltaic applications. The year 2015 witnessed an upsurge in the published research articles on perovskite solar cells (PSC) which is indicative of the potential of this material. Since the introduction of PSC the power conversion efficiency has reached above 22% in a relatively short period of time. However, the poor reproducibility in device fabrication and lack of uniformity of the PSCs performances is a major challenge in obtaining highly efficient large scale PSC devices. The aim of this paper is to present a brief review on the current status of perovskites based solar cell due to the use of different device architectures, fabrication techniques as well as on the use of various electron and hole interfacial layers (HTMs and ETMs). The review also discusses the basic mechanisms for device operation which provides better understanding on the properties of the various layers of device structures.
Journal of Physics and Chemistry of Solids
Abstract Environmentally stable and uniform silver:zinc bimetallic nano-composites (BNCs) was syn... more Abstract Environmentally stable and uniform silver:zinc bimetallic nano-composites (BNCs) was synthesized by co-reduction of silver:zinc ions from silver and zinc nitrates. The synthesized nano-composites were employed at the various layers of the device structure in the preparation of thin film peroveskite solar cell. Experimental evidences suggest that the nano-composite exhibited core-shell type structure which has important implication for surface plasmon resonance (SPR) absorption. Enhanced photo-currents have been measured from solar cells by employing Ag:Zn nano-particles as electron transport co-buffer layer. Which resulted in improved power conversion efficiency and short current density by 26% and 53%, respectively. The information gathered from the optical measurements of the nano-particles suggest that significant quenches in photoluminescence(PL) intensity was measured from Ag:Zn composite compared to monometallic Ag and Zn nano-particles which is attributed to enhanced carrier density in bimetallic phases. Scanning and tunnelling electron spectroscopes (SEM and TEM) were employed to investigate morphology, crystallinity and elemental composition of the nano-particles.
Deafness or being hard of hearing is one of the major hindrance of effective communication betwee... more Deafness or being hard of hearing is one of the major hindrance of effective communication between the hearing and the deaf. A deaf person can neither hear his voice nor that of other people and therefore cannot develop meaningful speech or language. Being deaf or hard of hearing limits one from getting or giving information [13]. In Kenya there are over thirty primary schools for the deaf with an average of a hundred and eighty students or less and a few smaller units of between thirty and forty students. It was the purpose of this project to help design and simulate an alarm system that can help deaf and hard of hearing students improve communication with their teachers and the rest of the people. This is because deaf students can learn to speak and make themselves understood if properly taught by skilled parents and teachers through the senses of vibration, touch, visual aids, kinesthetic( combined sensations by which position, weight and muscular position are perceived) and prop...
Physica B: Condensed Matter, 2016
Abstract The effect of interfacial buffer layers in organic photovoltaic cell (OPV) whose active ... more Abstract The effect of interfacial buffer layers in organic photovoltaic cell (OPV) whose active layer is composed of poly(3 hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend was studied. The electrical properties of OPV devices produced with and without interfacial layers are compared and discussed in terms of measured parameters of the cells. The charge transport properties showed significant difference on the mobility and activation factor between the two types of device structures. The life time measurements in the unprotected conditions are also presented and discussed.
Nano Hybrids and Composites, 2018
Organic and inorganic nanocomposites have been successfully used in the preparation of thin film ... more Organic and inorganic nanocomposites have been successfully used in the preparation of thin film organic solar cells with the view either to enhance the harvesting of solar energy or to assist in the charge transport processes. The optical absorption, conductivity and environmental stability of the nanocomposite are the main criteria that determine the suitability of the material for solar energy application. This chapter discusses the properties of a number of nanocomposite which are widely used in the preparation of various types of thin film solar cells.
Optik - International Journal for Light and Electron Optics, 2016
Physica E: Low-dimensional Systems and Nanostructures